And herman a



Bed. 19, 1922.

1 43 L. ESPENSCHlED ET AL. HIGH FREQUENCY TRANSLATING clRcuLTs.

HLED SEPT. 30.1919. 2 SHEETS-SHEET 1.

' INVENTORS AT ORNEY Dec. 19, 19220 L. ESPENSCHIED ET AL,

men FREQUENCY TRANSLATING omcuns.

2 SHEETS-SHEET 2- man HLED SEPT. 30, 1919.

min

ATTORNEY Patented Dec. 19, 1922.

sra'rns 1,438,987 rarnur orrica.

LLOYD ESPENSOHIED, 0F HOLLIS, NEW YORK, AND HERM'AN A. AFFEL, OF BROOKLYE', NEW YORK, ASSIGNORS TOAMERICAN TELEPHONE AND TELEGRAPH COMPANY, A

CORPORATION OF NEW YORK.

mennnnouiinciz TnAnsL rIuG "orncorrs,

Application filed September '30, 1919. Serial No 327,399.

To all whom it may comerml p Be it known that we, LLOYD Esrnnsci-lino and HERMAN A. Arr m, residing at Hollis and Brooklyn, in the counties of Queens and. Kings and State of New York,

respectively, have invented certain Improvements in High-Frequency TranslatingGiu cuits, of which the following is a specification. 3 i y This intention-relates to high frequency translating circuits, and more particularlyto arrangements for modulating currentsof v a rious frequencies;

its is well known, modulation of a pluraL ity of frequencies consists in the superposi tion of the input currents upon cachother, either in the modulator element; or at some point in the input side ofthe said element. By the term modulator element is meant any portion of an electrical circuit, the electrical constants of which maybe varied in accordance with signal ariations; thus, it may he a Xacuum tube in which the output resistance isvaried in accordance with grid potential, or an electric arc, the resistance-of which a function of the impressed voltage, or, it may he ai'eactance elemcnt such oi which is varied hya controlling circuit, or acondenser, the capacity oliwhiohmayhe controlled by varizition in the plate separation min the dielect ic constant. 7 1 p It is desirable, theretoreflo provide means for superposing'the two input currents so as to avoid loss oi energy and diininution'ott modulating efliciency arising trommutual shuntingeffects. There are, in general, two v ys whereby the input currents may be super ioscd so to be rendered mutually an indmtancc, the effective permeability of frequency. selection combined with the method of balance. h In Flgure 1, L represents a line adapter for the transmittal or low frequency currents,

such as for'example, telegraph currents. which is connected with a high frequency terminal circuit by means of arelay R havmg a network N adapted" to balance the line L This relay comprises balanced windings connected with the line and an armature 1, which is under the control of the said windings and adapted to apply impulses to the transmitting circuit. receiving circuit 2- is bridged across the midpoints of the halance'd windings of the relay so that impulses transmitted over the line L by the receiving circuitQ will not actuate the receiving relay 1%,. The low frequency output circuit 3 has inserted therein a low pass filtor F which is adapted to transmit low frequency'signaling currents which may he imT pressed upon'the input side of the modulator M by means of a transformer T The generator G may be any type of device adapted to generate high frequency sinusoidal oscillations, which oscillations may be impressed upon theinput side of the modulator M The filter F or its equivalent is inserted in the high frequency input circuit, in order to transmit high frequency oscillations, and suppress low trequency'currents. The output sideof the modulator M is con nected with the input side of the amplifier A by the transformer T The output circuit of the amplifier A is tuned and adapted to transmit oscillations of the resonant frequency'upon the output circuit 4. This output circuit is connected with a transmitting circuit TL which is in turn connected. with the main transmission line. ML by a transformer T The filters herein referred to may he of the general type illustrated and de: scribed in the U. S. Patents to George Campbell No. 1,227,113 and No. 1,227,114, hoth dated May 22, 19 17.

Qscillations received over the line ML and the receiving branch BL are impressed by the transformer T upon the resonantinput circuit 5 of the amplifier A The amplified oscillations are impressed by transformer T upon the detector D Bridged across the output side of the said detector is a high pass filter F which is adapted to shunt. the can rier frequency oscillations that pass through the detector D thereby preventing their passage into the low frequency circuit. Low frequency impulses which result from demodulation are impressed by the transformer T upon an input circuit containing a low pass filter F and the'windings of a polarized relay R The low frequency impulses applied to the said relay actuate the armature 6, and send impulses over the low frequency signaling circuit L to the receiving apparatus associated therewith.

In the operation of this circuit, low frequency signals arriving overthe line L will actuate the armature 1, and send a low frequency impulse over the circuit 3. The frequency of this impulse is such .as will pass through the low pass filter F and the impulselwill be impressed upon the input side of the modulator M by the transformer T Since the filter 11 is adapted to pass only high frequency oscillations, the low freqnency impulses impressed upon the input circuit by the transformer T will not be permitted to pass into the high frequency channel. High frequency oscillations set up by generator G will pass through the high frequency filterF; and be impressed across the inputside, of M These oscillations will not also pass into the low frequency circuits 3 on account ofthe presence therein of the low pass filterF It will be seen that the input circuits are rendered mutually non-interfering by 'means of the application of this method of frequency selection.

By the simultaneous impression of the signaling current and the carrier current upon the modulatingelement, the carrier current will be modulated thereby and the modulated oscillations will be amplified by the amplifier A and be impressed upon the output circuit 4, and transmitted over the transmission lines TL and ML. The received high frequency oscillations will be impressed by the transformer T upon the amplifier A and the resulting amplified oscillations will in turn be impressed upon the detector D Oscillations of the carrier frequency which may pass through the detector D together with the detected currents will pass into the filter F and be suppressed thereby. The low frequency signaling impulses resulting from demodulation will pass through the low frequency filter F and actuate the polarized relay 1. High frequency oscillations will not pass into .the circuit containing the relay R due to the presence of the low pass filter therein, which prevents the transmission of the high frequency oscillations. It will be seen from the foregoing that the input circuits are rendered non-interfering by means of suitable filtering devices inserted therein.

Figure 2 shows a way in which the method of frequency selection may be applied to a magnetic translating circuit. T represents pass filter a source of low frequency signaling current-s connected with an amplifier A whereby the amplified currents will pass through the low pass filter F and be impressed upon the iron core modulating device M by means of the winding 1. High frequency oscillations from the-source G, which may be of any well-known type of generating device may be impressed upon the amplifier A and the amplified currents passing through the high F will be impressed upon the modulator M by means of the winding 2. The third winding 3 of the modulator is connected with asource of current 13 by means of which the proper degree of saturation of the iron core of the modulator M may be maintained and a filter F is inserted between the source and the winding 3 to prevent shunting the low frequency voice currents and also the high frequency carrier current. A fourth winding 4: is connected with a tuned output circuit coupled with the antenna In the operation of this circuit, low frequency signaling currents set up by T are amplified by the amplifier A and pass through the low frequency filter F to the modulator M Simultaneously high frequency carrier currents produced by G and amplified by A pass through the high frequency filter F and are likewise impressed upon the modulator M It will be seen that high frequency oscillations cannot pass through the low pass filter F to the low frequency circuit, and similarly low frequency currents cannot pass through the hi 11 pass filter F to the high frequency gencra ug circuit. In this manner interference between the input circuits is avoided, and the modulated oscillations are transmitted by the winding 4: to the antenna circuit X.

Figure 3 shows a means for combining the method of frequency selection with the method of balance in order to avoid interference between the input circuits. A transmitter T is adapted to impress low frequency signals upon the common conductor of the modulator M by means of transformer T the low frequency signals passing through the low pa s filter F Simultaneously, high frequency oscillations from the source G passing through the high pass filter F are impressed by the transformer T upon the input side of the modulator M ihis modulating device may be of any well-known balanced typesuch as, for example. the balanced duplex modulator described in the patent to John ll. Carson, 1343.308, dated June 15 1920. It will be seen that the low frequency currents set up by the tra sformer T in the common condu tor of the modulator M will low in opposite directions in the winding of the trans former T and therefore, will produce substantially no effect in the generating circuit G. and similarly high frequency oscillations impressed across the input side of themodu lator will produce substantially no effect in the windings of the transformer T Since the filter F is adapted to pass only low frequency oscillations, the high frequency oscillations arising from the generator G will not be transmitted into the. low frequency transmitting circuit.

Figure 4 shows another means of combining both methods of preventing interference between input circuits of a demodulating element. The low frequency I circuit has therein a transmitter T and a low pass filter F The low frequency signals set up in this circuit are impressed across the winding 1 upon the central arm of the core of theward and half downward, which creates a neutral condition preventing induction of currents in the winding 2 uponthis core. 1n a similar manner the, flux setup by the highfrequ'ency winding 2 will not induce high frequency oscillations in the low frequency circuit. Filters F and F interposed in the low frequency and high frequency input circuits respectively prevent the passage of, high frequency and low frequency currents through filters F and F respectively. If lowfrequency signaling currents are impressed upon the winding 1 upon the central arm of the core, the resulting flux will change the permeability of the core with respect to the winding 2. The high frequency current set up in the winding 2 by means i of the source G willbe modulated accordingly and the modulated high frequency current will be impressed upon the winding 3 of the output circuit L This arrangement shows means for combining frequency selective devices with a balanced ironcore modulator, thereby assuring ahigher degree of freedom from interference of the oscillations in one of the input circuits by those in the other input circuit. c a

Figure 5shows the application of this invention to a circuit in which an arc constitutes the modulator element. A represents an are between the electrodes 1 and 1, across which a direct currentfrom the battery B is applied through the reactance coils C, and Oscillations are set up in the output circuit 2 which embraces the antenna X. Low frequency signaling current in the transmitter T may be impressed upon the circuit 3 which is bridged across the electrodes 1 and'l. A filter F' isinserted in the low frequency circuit 3 adapted to transmit the low frequency signals of, for example, 10 to 2500 cycles, and will prevent the transmis sion therethrough of frequencies below 10 and above 2500 cycles. High frequency oscillations will be set up in the circuit 2 in a manner that is well known, and these high frequency oscillations may be modulated by the low frequency current impressed upon the circuit 3 by the transmitter T These low frequency signals will pass through the filter to the modulator device,

namely the arc but high frequency oscillations of the circuit 2 may not be transmitted through the filter F into the low frequency signaling circuit. This circuit arrangement shows the meanswhereby the low frequency input circuit may be protected from inter ference by the high frequency OSLlliiiilOi'lS of the oscillating circuit, which the low frequencies are adapted to modulate.

Figure 6 shows an arrangement for a balanced arc modulating system, in which the method of frequency selection is also applied in order to assure a higher degree of protection of'the frequencies in one input circuit from interference by currents in the other input circuits of the modulating device. In the circuit arrangement A and A represent two arcs which may be of any well-known type connected with a common source of direct current B and having reactance coils C and C associated in the d rect current circuit. The output circuit is represented by the antenna X, which has connected therein one of the windings 3 of the triple-winding transformer T The other two windingsof the said transformer are connected in series with the arcs, each winding being individual to an arc circuit. These windings of the transformer are so arranged and designed that equal currents in the same direction in each arc conductor will cause no resultant action in the winding 3 which is connected with the antenna Under these conditions the action of the two arcs in parallel is equivalent to that of a single are connected across the source of direct current B and its frequency of oscillation will be determined by the inductance L and the capacity K Bridged across the arc conductors is a low frequency circuit 4'. upon which signaling currents from the transmitter T may be impressed. Inserted in the low frequeny circuit is afilter F7, or its equivalent which is adapted to transmit frequencies within the range of 10 to 2500 cycles. inserted in the two are conductors. between the point where the low frequency signaling cirvaried accordingly,

lations having a frequency between lu and 25520 cycles and to transmit frequencies belor: l0 and above 2500 cycles.

Having in mind the foregoing description the invention will be made clear from the following description of its mode of op eration:

Direct ci rent will flow from the battery B, through each of the arcs A and A and through the windings 1 and 2, which are re spectively connected with the arcs A, and A High frequency oscilla ons resulting in a in. ner 1 is well-hr wn will he set up in the high frecucncy oscillatin circuit which lf-l lllllr es the inductance li ca pacity K and the parallel conducting paths containing the arc A the coil 1 and the are A. and'the coil 2 respectively. These oscillations will pass through the filter F since it is designed to transmit high frequency oscillations. Since these currents are in the same direction in each of the coils l and 2, and of the same magnitude. no oscillations will be set out in the outp "t circuit X. If, however, low frequency signaling; currents are impressed across the arc conductors by means of the circuit l, the high frequency oscillations in the coils l and 2 will and th modulate cillations will be set up in the transmitting circuit X, since the transformer T, is no lone'er balanced. .lnview of the presence of the filter F which suppresses frequencies bill? between 10 and 2500 cycles, the low.fre

quency current applied acro s the are conductors will not be short circuited tl the unction of the two are conductors with one side of the direct cur 'ent circuit and tire oscillating circuit. Furthermore, it will be seen that the filter F which is the type adapted to transmit frequencies between 10 and 2500 cycles will prevent high frequency oscillations from being;- impressed upon the low frequency transn'iittinocircuit. This circuit snows means whereby each input circuit of a balanced arc modulator may be protected from interference by frequencies which are foreign to that circuit.

it will be noticed. that certain of the circuit arrangements shown in the dr 4 are connected with an output circuit con sisting of a metallic transmission circuit, and other circuit arrangemei shown in the drawings have their output side connected with a radio antenna. It. is to be understood that the various circuit arrangements are not liinited tovthe particular type of output circuit shown, but that the output side of any circuit arrangement may be connected either with a metallic transmission line or with radio antenna without departing from the scope of the invention.

Although this invention has been shown as embodied in particular forms and organizations of parts, it is to be understood that it is not limited to such forms and organizations, but may be embodied in other and different forms within the scope of the appended claims. I

float is claimed is:

1. In a high frequency signaling system, the combination of a translating device, an input circuit adapted to impress carrier current upon said translating device, a second input circuit adapted to impress signaling currentupon said translating device and means associated ith each input circuit for protecting the currents in each input circuit against interference by current of the oth r nput circuits.

2-. In a high frequency signaling system, the combination of a balanced translating circuit, a plurality of input circuit-s adapted to impress a plurality of frequencies upon said translating circ it, and means associated with each input circuit adapted to protect the frequencies of each input circuit frominterference by the frequencies of the other output circuits.

3. In a high frequency signaling system, the combination of a balanced duplex translating circuit having; thermionic translating devices associated therewith, input circuits adapted to impress a carrier current and a signaling current upon said translating circuit, and frequency selecting means assoc1 ated with each input'circuit to exclude from each respective circuit frequencies foreign LT n l. in ahigh iiequency signaling system, tne coinlunation of a translating device, a plurality of circuits constituting respectively sources of carrier current and of ling current, each of the said circuits having a'iilter associated therewith to prevent mutual reaction between the respective input circuits.

5. In a high frequency signaling system, tl' e combination of a modulation circuit, a source of low frequency current, a source of carrier frequency current and means interposed between the said modulation circult and each'of said sources to prevent current from one source interfering with current from said other source.

6. In a high frequency signaling system, the combination of a modulation circuit, a source of low frequency current. a source of carrier current and frequency selectingmeans inserted between said circuit and each of said sources adapted to transmit readily frequency produced by the source with which the said selecting means is connected.

7 i. in a high frequency signaling system. the combination of a translating circuit, a circuit having a source of current of one frequency, a circuit having a source of carrier of current, each of said latte-r circuits ha int; selecting networks adapted to transmit frequency of its particular source, and

eacl: in said latter circuits being so coir nected with said. translating circuit as to prevent current in one of said sources inducing current in the'circuit of the other of said sources. P

S. In a high frequency signaling systeni the combination of a balanced duplex translating circuit, a source of signaling current, a source of. carrier current and a filter connected between saul trai' slatlng circuit and;

each of said sources.

the combination of a radio l re uene 1 transmitting circuit, a translating circuit having i a plurality of input cii'cuits oi'ie of said input cir iits having conncctcil therewith a source (iii 7 of said input circuits a source of carrier frequency, and a filter individual to and connected with each input circuit to transmit current only of the frequency which characterizes that particular circuit.

in testimony whereof, we have signedour a names to this specification this 29th (lay of i'jeptember 1919. 9. In a high frequency signalingsystem,

LLOYD ESPENSCHIED. HERMAN A. AFFEL.

signaling frequency and another; 

